Lasers (acronym for light amplification by stimulated emission radiation) or optical lasers (acronym for microwave amplification by stimulated emission radiation) are light amplifying devices which produce high intensity pulses of coherent monochromatic light concentrated in a well collimated beam commonly called a laser beam. There are several uses for such laser beams. Since the beam can be sharply focused, it can produce energy densities suitable for drilling, welding, cutting, etc. One potential application of laser beams is in the field of communications where the optical spectrum represents almost limitless bandwidth and information carrying capacity.
It is desirable to have lasers which are operable at many different wavelengths in the light spectrum including infrared, visible and ultraviolet regions. Since the wavelength emitted by a specific energy transition in a laser medium is tunable over only a small portion of the spectrum, it is necessary to provide a number of materials adapted for use as active laser media at various light frequencies. Certain organic dyes in solution can operate as "liquid" or "organic dye" lasers. Of the range of materials useful as lasing media, organic lasing dyes provide certain advantages. A wide range of organic dye lasers is available to provide stimulated emission (lasing) over a broad range of the spectrum. Secondly, organic dye lasers are generally capable of being tuned to emit over a range of wavelengths. Thirdly, organic dye lasers provide an economical lasing medium when compared to gas and solid lasers, and they do not suffer from disadvantages such as cracking and optical imperfections that are particularly associated with solid lasers.
The ability to selectively tune organic dye lasers derives from the broad band fluorescence characteristic of the dye. Such lasers can be "tuned" to emit at wavelengths along substantially the entire fluorescence band of the dye by interposing a dispersive element, such as a diffraction grating or a prism.
It is known that certain coumarin dyes are capable of lasing action. However, no coumarin dyes are known that include (1) a phosphorous atom in the coumarin ring, or (2) a phosphorous-containing substituent on the coumarin ring.